Roman Britain in 91 AD is a raw frontier province, a troublesome part of the mighty Empire ruled by Domitian Caesar. Though it is almost fifty years since the legions invaded, many native tribes still hate their conquerors and seize any chance to harass the Roman settlers who are flocking in to colonise the new province. Tension is especially high in the north, where Aurelia Marcella, a young innkeeper from Italy, runs the Oak Tree Mansio on the road to York.

A string of savage murders disrupts her peaceful life, and she and her Roman friends find themselves under attack from a secret native war-band, the Shadow-men, whose aim is to drive all Romans out. A traveller, Quintus, is nearly killed close to the inn, and he and Aurelia must track down the rebel warriors and identify their mysterious masked leader, the Shadow of Death. Their investigations bring them into personal danger from ruthless killers and devious deceivers. Can they find and destroy the Shadow of Death before his campaign of terror turns into open rebellion, so that all Romans must get out or die?